FIG. 1 is a diagram showing an example of a conventional charge control circuit that uses a switching power supply and a linear voltage regulator together (see, for example, Patent Document 1).
The charge control circuit shown in FIG. 1 attempts to improve power efficiency by operating either the switching power supply or the linear voltage regulator in a switching manner with the battery voltage of a secondary battery. The detection of a charge current at the time of constant current operations is performed using a voltage difference between both ends of a resistor RSNS connected in series to the secondary battery.    Patent Document 1: JP-A-2007-14163
However, due to the resistor used for detecting the charge current, a current flowing through the resistor disadvantageously causes loss. Moreover, when the resistance value of the resistor is made small to reduce the loss due to the resistor, it is necessary to use a high-accuracy operational amplifier.